Ferroelectric random-access memory (FeRAM) cells have been considered for use in many memory arrays. FeRAM cells include a ferroelectric material having a switchable polarization responsive to application of an electric field (e.g., a bias voltage). The polarization state of the ferroelectric material in the FeRAM cell may be used to determine a logic state (e.g., a 1 or a 0) of the FeRAM cell. After the bias voltage is removed, the polarization of the ferroelectric material may remain. The FeRAM cell is therefore, non-volatile, eliminating the need to refresh the memory cell periodically.
Conventional FeRAM cells under an applied field theoretically exhibit a square hysteresis loop 102, as illustrated in FIG. 1, since atoms of the ferroelectric material transition between two equally favorable states. The FeRAM cell is switched from one operational state to another operational state by exposing the FeRAM cell to a switching bias voltage. For example, the ferroelectric material may be exposed to a positive voltage to switch the polarization of the ferroelectric material to a first direction. At a large enough positive voltage (characterized as the positive switching voltage), the polarization of the ferroelectric material switches from a negative polarization to a positive polarization. To switch the FeRAM cell to another state, the ferroelectric material is exposed to a negative switching voltage to change the polarization of the ferroelectric material to a second, opposite direction. Conventionally, the positive switching voltage and the negative switching voltage applied to a conventional FeRAM cell are equal in magnitude (e.g., have the same absolute value, also referred to herein as a symmetric biasing scheme).
Unfortunately, many FeRAM cells require utilization of a high bias voltage to switch between different polarization states. Any power savings realized by the non-volatility of the FeRAM cell relative to a DRAM cell are offset by the high bias voltages that must be applied to switch the polarization state of the ferroelectric material. Thus, exposing the ferroelectric materials to the higher voltages increases power consumption of the FeRAM cells, increases operating costs, and may also decrease the useful life of the FeRAM cells.